I've been geeking out lately on drone oscillators, using Schmitt triggers. This week I built a 4 oscillator thing with switchable mixing. Very low parts count and easy to build. Sounds great through a digital reverb and delay pedal into stereo!

Also wrote up an article describing this and other CMOS circuit fragments.

Wow - I've been playing with drones the last week or so, too. I also used 40106 osc's - 4 of them at audio rates, one LFO. 4011 psuedo ring mod, synch routing, and a couple of WSG filters with vactrol's for modulation by the LFO....

Just the 40106's provide great fun....adding filters and other stuff does good things too.

Wow - I've been playing with drones the last week or so, too. I also used 40106 osc's - 4 of them at audio rates, one LFO. 4011 psuedo ring mod, synch routing, and a couple of WSG filters with vactrol's for modulation by the LFO....

Just the 40106's provide great fun....adding filters and other stuff does good things too.

Can someone explain me why in this building ( or in most of 4017 based sequencer for example) we need 1na914 diodes and no 1na4148 ? Can we use 1na4148 in the heterodyne space explorer ?

What would it change ?

Nothing. The '4148 can handle more than twice as much current than the '914, but that is of no concern in this or most other circuits._________________"I am endeavoring, ma'am, to create a mnemonic memory circuit... using stone
knives and bearskins." -- Spock to Edith Keeler

I must say that I've never seen anywhere that charges more for higher values of pots. In fact I've never seen anywhere that has different prices for different values at all.
Also, larger value caps tend to be less stable to temperature changes, and require more "wearing in" than lower value caps.
I don't mean to be contrary, just stating my experience. _________________What makes a space ours, is what we put there, and what we do there.

Hey all. I've been working on one of these, following the schematic in the first post. I'm mixing using diodes. For some reason, all I can get it PWM. Is that all I'm gonna get, seeing as I'm mixing signals, or should I be able to get straight audio mixing as well?

Hi !!
I've just build the heterodyne white noise part, and it seems to be a very "shy" white noise source...

Well, i used a 4049 as preamp, and i didn't use 2n3904, but bc547b instead for transistors...

Is it normal if it's not so loud ? Did il make mistakes in building this part as a stand alone ?
Thanks for any answer !

Most any general purpose npn transistor can be used in this type of noise circuit, but Q1 should be socketed so that you can select a transistor that makes the most noise.

I'm don't know that the 4049 can be used as an amplifier, but I do know that the 4069 (74C04,) can be.

Another thing you might try to boost the noise is replace diode D5 with a capacitor. I don't see why there needs to be a diode there.

If you still can't get enough noise, put back diode D5 and try one of the circuits below. You should have two 40106s left over. Try the top circuit (from National Application Note AN-140,) first. If that still doesn't get you enough noise, stick another transistor in front of the schmitt trigger, as in the bottom circuit.

And as long as I'm putting my 2cents in here... I must correct one bit of information in beavis' otherwise excellent article. Experiment 6 states "Diode D1 keeps oscillator two from feeding back into oscillator one." If anything, the direction D1 is pointing allows oscillator two to feedback to oscillator one, but that's not what's going on in this circuit. When U1a output is low, it pulls down U1b's input, preventing it from oscillating. When U1a output goes high, the diode blocks the DC level from reaching U1b's input, allowing it to oscillate. In other words, oscillator 1 gates oscillator 2 off/on.

I've been building the space explorer. I noticed that if I turn the volume on one of the oscillators all the way down it will mute all of the oscillators. Is this normal, or am I doing something wrong?

It could be (somewhat) solved by placing a resistor after each volume pot (VR3, VR5, VR7, VR9) at the wiper. This way not all post potmeter signal gets shunted to ground when one of the outputs is.

Another option would be to insert a resistor between the pots and ground. This way non of the oscillators can be totally grounded. An other possibility is using a combination of both options. Interactions are inevitable with both methods I suppose. That could be tackled with separate buffers after the oscillators maybe, but then, interaction is good, leading to the drone character of the design.

Edit: A resistor at the wipers is the best method I expect.

Disclaimer: electri-fire's answers are more often based on his limited knowledge of theory than on actual experience.

Another way is to turn the pots around, so the resistance of the pot is always presented to the output, then the oscillator is connected to the wiper. At the top, you have the same situation as the other way around. At the bottom the oscillator is connected to ground. (Maybe add a resistor before the wiper to limit the current to ground out of the 40106)_________________What makes a space ours, is what we put there, and what we do there.

It may be 1.24AM..... BUT..... Just breadboarded the Heterodyne Space Explorer. Pots may be poking out everywhere and I'm having difficulty distinguishing what's what, but what a great thing this is! I was running it through a flanger (my latest favourite effect) and a reverb but it almost doesn't need the flanger! This is really addictive stuff. The key is balancing the four oscillators to get that wavering tone real slow. May need fine tuning pots added somehow.... Hmmm....Not even sure if pots are the right interface for the creation of these haunting tones. Maybe the movement of stones in a sandbox.... or harnessing the wind... or balancing something might be more apt. Anyway, the sky has just fallen on my head and I'm going to tell the King....

Now I really won't get to sleep! Having too much fun! Oh, yeah... I reversed the pots a la Krunkus/electri-fire method. haven't added the extra resistors yet. Might try that next. Have to test the diodes too! Still on resistor mode!

NEVER EVER pull a working breadboard apart until you have something working on stripboard or whatever you use!! I had such a beautiful thing for a while..... but now it's gone. Story of my life! F#$% it!

Oh look.... don't even bother reading this.... I'm just going mad! Besides I don't even know which parts the + and - are on a 9V battery!

Carry on.... I'm not going to sleep until this is resolved! I just want my drones back.....

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